This invention relates, generally to print element apparatus and more particularly to a print element mounting apparatus used to accommodate quick and easy interchange of a print disc from a selector shaft in a printing machine or the like.
Printing machines and particularly typewriters are becoming increasingly more versatile in their performing capabilities. Many of today's typewriters are being manufactured of the kind employing a single print head or element which contains thereon a complete arrangement of alphabet characters which are selectable from corresponding keys of a keyboard. There are basically two different common forms of single print elements known and widely used in the art. They are usually referred to as "ball" or "disc" type elements which generally describes their overall appearance. A major advantage offered by single print element typewriters, over bar typewriters, is that the element may be adapted with a coupler to conveniently facilitate interchange among different elements to meet a particular work need or desire or to replace a damaged element. For example, a business letter requires an element having alphabetical characters, which are available in different styles and sizes, such as pica and elite. Technical work would require an element containing special characters such as mathematical or scientific notations and symbols.
The prior art discloses many varied and different coupler arrangements for enabling detachable mounting of a print element in a printing machine. One example is disclosed in U.S. Pat. No. 4,036,348 entitled FIXING DEVICE FOR A TYPE-CARRIER DISK granted July 19, 1977 to Guerrini. This patent teaches four individual fixing members pivotally mounted and spring-biased on a specially formed flange fixed on a selection shaft. The print disc has an aperture that squeezes the four members together in response to attaching and removing the print element. The Guerrini patent has many disadvantages including its overall complexity wherein many costly, relatively small and difficult to assemble parts are employed. Since the disc coupling members are assembled directly on the printer shaft, a complete machine shut-down is necessary in the event service maintenance is needed to repair damaged or worn members of the disclosed fixing device.
Two other examples of a disc coupler device are disclosed in U.S. Pat. Nos. 3,878,929 granted Apr. 22, 1975 and 3,986,593 granted Oct. 19, 1976; both invented by Orlens et al. Both aforementioned patents utilize a plastic coupler which is molded as part of a disc. Each molded coupler includes a shaft-grasping configuration connected to the disc via flexible arms. In order to attach or remove the disc, the arms need to be bent by applying finger squeezing pressure which may be an initiating stress to the fingers. A resilient memory plastic material is utilized to form the flexible arms. This kind of plastic inherently tends to lose some of its resiliency over a period of time after many uses and, therefore, the arms may not completely return to their original relaxed state for positively gripping the shaft. Though in terms of parts required, these integral one-piece couplers are relatively simple. However, the element itself is highly complex and difficult to mold which leads to manufacturing problems.
The present invention avoids disadvantages found in these and other known prior art print element couplers and provides a print element equipped with an extremely simple mounting apparatus so as to readily enable one to quickly attach and remove a print disc in a comfortable convenient manner.